It is well known that sunlight purifies air. More specifically, it is the light in the UV-C wavelength range (around 260 nm) that purifies air. UV-C light is germicidal by deactivating the DNA of viruses, bacteria, and dust mites. However, this natural germicidal process doesn't occur indoors. Many UV-C germicidal systems have been invented for indoor uses such as UV-C sanitizing wands, UV-C housing used inside HVAC systems, and etc.